1. Field of the Invention
The present invention is in the field of wastewater treatment and specifically relates to an improvement in apparatus for use in destroying dissolved organic contaminants in the wastewater. The design of the apparatus is described more fully in U.S. Pat. No. 4,897,246 referred to above, and the contents of that patent are incorporated by reference into the present application.
2. The Prior Art
As described in the aforesaid patent, the water treating apparatus includes an oxidation chamber in which the wastewater is subjected to intense ultraviolet radiation as well as oxidation by hydrogen peroxide that is added to the wastewater. The ultraviolet radiation is generated by a number of ultraviolet lamps that extend coaxially through quartz tubes that, in turn, extend through the walls of the oxidation chamber.
One of the problems that has been encountered in the use of the oxidation chamber is a tendency for the quartz tubes gradually to become coated over with a film of a dark colored slime. This fouling of the quartz tubes is undesirable because it interferes with the transmission of the ultraviolet radiation from the lamp to the wastewater. When the fouling becomes sufficiently serious, it is necessary to interrupt the treatment of the wastewater to remove and clean the exterior of the quartz tubes. Clearly, it is desirable to minimize such interruptions in the operation of the oxidation chamber.
A solution to the problem was not found in the prior art. For example, in U.S. Pat. No. 4,694,179, Lew, et al. described a sterilizer in which ultraviolet light is used to destroy bacteria and other germs that contaminate a fluid medium. In that apparatus, the ultraviolet lamp is enclosed within an ultraviolet-transparent tube which is described as being composed of a hard glass. The problem of fouling is not discussed, and no solution to it is suggested by the patent.
In U.S. Pat. No. 4,273,660, Beitzel shows a fluid treatment chamber of annular cross section, with an ultratreatment violet lamp extending axially through the chamber. Thus, the tube that surrounds the lamp also serves as a wall of the chamber. The problem of fouling is not discussed, and it would appear to be difficult to clean the wall by mechanical means.
In U.S. Pat. No. 3,485,576, McRae, et al. describe an ultraviolet apparatus for disinfection of aqueous liquids. In their system, the envelope of the ultraviolet lamp is in direct contact with the liquid. The problem of attenuation of the ultraviolet radiation by a buildup of slime on the lamp is described, and the use of manually-operated wipers is said to be known. The solution patented by McRae, et al. is to pass a direct electric current between the plasma in the lamp and an electrode located in the liquid external to and out of direct physical contact with the outside surface of the lamp so as to produce a negative charge on the outside wall of the lamp, whereby the charged colloidal particles are electrically attracted to an external anode grid where they are deposited. The present invention makes use of an entirely different approach from the electrical technique used by McRae, et al.